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Absence of fluid-ordered/fluid-disordered phase coexistence in ceramide/POPC mixtures containing cholesterol
M Fidorra1, L Duelund, C Leidy
1MEMPHYS-Center for Biomembrane Physics, University of Southern Denmark, Odense, Denmark.
Biophysical Journal
|March 28, 2006
Summary
This study reveals that temperature influences the lateral structure of lipid bilayers, showing gel-phase domains in POPC/ceramide mixtures. Cholesterol addition shifts this to a gel/liquid-ordered phase coexistence, forming unique membrane patterns.
Area of Science:
- Biophysics
- Membrane Biophysics
- Lipid Bilayer Dynamics
Background:
- Lipid bilayers are fundamental to cell membranes.
- Understanding lipid-protein interactions and phase behavior is crucial for cell function.
- Ceramides and cholesterol significantly modulate membrane properties.
Purpose of the Study:
- To investigate the effect of temperature on the lateral structure of ceramide-POPC lipid bilayers.
- To examine the influence of cholesterol on these lipid mixtures.
- To reconcile discrepancies in previous phase coexistence observations.
Main Methods:
- Differential scanning calorimetry
- Fourier transformed infrared spectroscopy
- Atomic force microscopy
- Confocal/two-photon excitation fluorescence microscopy with LAURDAN GP
Main Results:
- Observed broad gel/fluid phase coexistence with micrometer-sized gel domains in POPC/ceramide mixtures.
- Resolved discrepancies in LAURDAN GP measurements between microscopy and bulk fluorometry.
- Cholesterol addition induced a transition to gel/liquid-ordered phase coexistence, unlike other ceramide mixtures.
- Identified a critical cholesterol concentration leading to a unique three-region lateral membrane pattern.
Conclusions:
- Temperature significantly impacts ceramide-POPC lipid bilayer lateral organization.
- Cholesterol plays a key role in dictating phase behavior and domain formation.
- The study provides new insights into lipid raft formation and membrane heterogeneity.
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